Get batch configuration fields from config file

[dchaley]

This adds a --configuration flag to the job launchers, which refers to a JSON file that we merge into the base job parameters. The config overrides whatever the base job says.

Use this to specify a network, subnetwork, service account, etc.

Paired with @WeihaoGe1009

Fixes #284

[dchaley]

Hi @bnovotny using this config approach, you can have a config file (see example-config.json) that specifies the fields you need. Then you'd just add --configuration=/path/to/your/config.json to the job launcher.

(Maybe we can put config in some well-known location to load automatically……)

[bnovotny]

I just used this along with run-qupath-job.py and everything looks good! The only tricky part for me is remembering all the arguments 😅 Thank you so much @dchaley and @WeihaoGe1009!!